Fluorescent chemical sensors for small organic compounds will be developed. Chemical sensors are synthetic probes which produce a visible signal upon interaction with a specific analyte. In the biochemical community, these probes have been used as sensitive, nondestructive methods for quantifying the concentration of a particular analyte in cells. Chemical sensors have played a pivotal role in unraveling the cellular function of a number of metal ions, most notably cell calcium. Similar fluorescent sensors for organic molecules have not reached this level of success. The specific aims of this research are to develop novel chemical sensors for neurotransmitters and neuromodulators. This is an important problem with broad ramifications. This project will produce sensors for glutamate, aspartate, lysine, and the catecholamines which function under physiologically relevant conditions of pH and salinity. Furthermore, fluorophores which are pH dependant will be produced to expand the utility of this class of sensors. Biological studies will be performed with the aid of collaborators in which cells will be stained with the fluorescent sensors and the location and concentration of neurotransmitter will be measured.